Low speed fuel pump circuit open

[emt7173]

I hope someone can help. I have a 89 SHO that is showing code 59. It ran great, filled the tank up to make a trip, made one more stop and it would not start. I have changed the fuel filter, the fuel pump, the screen that goes on the fuels pump and the plugs. Still no luck. Here is confusing part, i sold the car not running, they took it home and played with a wire and it started right up ( they said it was a blue wire ) they drove it for 3 weeks with no problems and then i had to repo it, drove it for 2 days and then it did it again, i am out of ideas can anyone help. any input would be great.

 

[projectSHO89]

Low speed fuel pump relay is in the relay box under the radiator sight shield. Individual relays are not easily replaced. It also uses the dropping resistor mounted on the top center of the firewall.

Steve

 

[schwagman85]

What does this dropping resistor do?

 

[SHOZ123]

schwagman85 ......... What does this dropping resistor do?

Lowers the voltage to slow down the fuel pump.

IIRC this is eliminated in latter SHOs. You could possibly use the low speed relay coil trigger signal from the PCM to also trigger the high speed fuel pump relay.